1. Field of the Invention
The present invention relates to an electromagnetically controlled fuel injection valve.
2. Description of the Related Art
A fuel injection valve which is composed of a movable core driven by an electromagnet coil against biasing force of a spring and a stationary core is disclosed in JP-U-60-88070 and JOURNAL OF NIPPONDENSO TECHNICAL DISCLOSURE BULLETIN No. 64-053. JP-U-60-88070 discloses a valve body which has a sintered hard surface to increase mechanical strength. NIPPONDENSO TECHNICAL DISCLOSURE BULLETIN No. 64-053 discloses a moving unit in which a valve body and a movable core are molded with compound of resin and soft ferrite.
However, the thickness of the sintered surface of the valve body disclosed above can be several tens of micro meters at most, and it is difficult to keep the hardened surface if the valve body is machined to have precise finished sizes. On the other hand, the moving unit molded with the resin and soft ferrite compound does not have sufficient hardness to ensure high mechanical strength.